This invention relates to a tape recorder and more particularly to a tape recorder comprising a reel mechanism provided with a pair of one-way clutches. Various types of tape recorders are known in which the rewind of a magnetic tape is carried out by causing a takeup reel to act as a supply reel and also a supply reel to act as a takeup reel through the slide of an idler. However, a tape recorder using an idler has the drawback that an idler changeover mechanism is required, enlarging the size of the tape recorder and complicating its arrangement. To eliminate this drawback, a tape recorder reel mechanism has been proposed which utilizes a one-way clutch. With a tape recorder reel mechanism provided with a one-way clutch, balls made of, for example, steel are disposed in a space defined between a drive disk and driven disk such as a clutch plate, on the periphery of which vortically shaped notches are formed. The rotation moment of a motor is transmitted from the drive disk to the driven disk by means of the balls. The tape recorder has to be properly operated even in an inclined state, or, in an extreme case, even in an overturned state. With the known tape recorder, the balls which are set free gravitationally roll on to abut against the periphery of the driven disk, possibly failing to act as frictional members in a space defined between the drive and driven disks. Further with the conventional tape recorder, the rotation moment of the motor is transmitted to the drive disk by means of an endless belt. However, the endless belt has the drawback that it should have a prescribed thickness, presenting difficulties in reducing the thickness of a reel mechanism and moreover is handicapped by unsatisfactory temperature characteristic.